Why did other civilizations not build pyramids?

Seven ancient sites believed to have been built by aliens

On a dry high plateau, a good 300 kilometers southeast of Lima, more than 800 straight, white lines run seemingly arbitrarily through the Peruvian desert. There are also 300 geometric figures and 70 depictions of animals such as spiders, monkeys and hummingbirds.

The longest of these lines run dead straight for kilometers. The largest figures are almost 36 meters in diameter and can best be viewed from the air. Scientists suspect that the Nazca Lines are up to two millennia old. Because of their age, size, visibility from above, and the puzzles they pose, the lines are often cited as one of the finest examples of the work of aliens on Earth. How else could an ancient culture have been able to create such huge images in the desert without flying? And why?

It turned out that the how is pretty easy to understand. The enigmatic images called geoglyphs are created when the top, rust-colored layer of the stones is removed, exposing the lighter, white sand underneath.

The why is a bit more difficult. The figures were first examined at the beginning of the 20th century and it was initially assumed that they were related to star constellations or solstices. However, recent research suggests that the Nazca Lines point towards ceremonial or ritual sites that have been associated with water and fertility. The lines can be seen not only from the air, but also from the surrounding hills.